Which statement about SSD conditioning is true?

• A. An SSD condition is one in which the aggregate contains only small amounts of free water on its surface.
• B. Shaking the basket to release any entrapped air as it is placed in the water bath is not recommended due to potential sample loss.
• C. The specified time period for the sand to soak in the water is 24-48 hours.
• D. Samples dried past the SSD condition must be immersed in water for 30 minutes prior to resuming the process of surface-drying.

Answer: (D)

SSD conditioning means the aggregate pores are filled with water while the surface has no water film, so the material is saturated but not wet on the outside. This state is essential because free surface water or dry pores would skew mass and absorption measurements.

If a sample dries past this condition—becoming drier than surface-dry—the interior is no longer fully saturated. In that case you need to re-saturate by immersing the sample in water for about 30 minutes before you resume the surface-drying step. This re-establishes the saturated interior and dry surface, ensuring subsequent measurements reflect the correct condition.

The other statements don’t fit the standard practice. SSD should have no surface water film, not just a small amount of free water. Releasing entrapped air is typically done to help achieve true saturation, not avoided, so shaking in a way that prevents sample loss wouldn’t be the recommended approach. And while soaking time is involved, the specified period and procedure are defined so the material reaches SSD reliably; 24–48 hours isn’t the precise, universally prescribed window for this context.